In many types of bacteria, cell to cell recognition is a key feature of pathogen virulence. Accordingly, methods for the extraction and purification of carbohydrates and proteins from cellular membranes, followed by reconstitution of cellular components into stable hydrophobic matrices has been widely used. Due to the complexity of biological membranes, cell surface components are often arranged in artificial membranes such as liposomes.
Outer membrane proteins from bacteria have been incorporated into liposomes for vaccines and the immune response of the resulting liposome preparations is known in the art. Liposomal formulations of antigens have significant advantages in vaccine formulation over cell-based formulations since they avoid safety concerns that may arise from attenuated or killed pathogens. However, methods of liposomal formulations of cell surface components still have limitations as vehicles for displaying cell surface proteins and lipids in a stable membrane-like environment. First, since cell surface components typically reside in the hydrophobic bilayer, the solubilization and purification of these substances from the membrane often results in denaturation of the protein. Second, it is unclear that insertion of the purified protein into the membrane of a liposome results in the presentation of the protein in its ‘natural’ form, especially in the case of denatured components.
Finally, liposomal formulations are limited by the general physicochemical characteristics of the liposomes themselves. The production of liposomes requires either sonication or passage through a membrane, and these processes result in the addition of mechanical stress to the system that also may lead to denaturation of sensitive biological components. Liposomal formulations prepared by either sonication or membrane extrusion are very heterogeneous in size, with distributions ranging from 300 nm to 20 microns. Finally, liposomal formulations are difficult to maintain in long term storage because they often precipitate within days of creation due to their inherent thermodynamic instability, typically compounded by additional instability in biological media due to pH and ionic strength issues.
In addition to liposomal preparations, current methods of making multivalent vaccines against Neisseria involve removal of lipooligo and lipopolysaccharides (LOS and LPS respectively) specifically because of their toxicity and immunological problems. van der Waterbeemd et al., Vaccine 28 (2010) 4810-4816 discloses that outer membrane vesicles used as vaccines maintain a residual amount of LPS (only about 1%) but are needed to adjuvate the immune response. The removal of LPS, however, also depletes the amount of lipoprotein that exists in the vesicles and reduces immunogenicity.
In contrast to van der Waterbeemd et al., the present disclosure addresses the limitations of vaccine and composition delivery via liposomes by using artificial membrane components from catanionic surfactants that package pathogen antigens and antigens associated with hyperproliferative disease, such as cancer. The vesicles also protect membrane-bound antigens from degradation as well as cloak or reduce the toxicity caused by bacterial lipopolysaccharides and lipooligosaccharides.
Francisella tularensis is an immune-evasive coccobacillus that causes tularemia disease in humans and animals. Francisella tularensis is classified as a Tier 1 agent. To date, there is no vaccine for Francisella tularensis approved by the FDA. Limitations in Francisella tularensis vaccine development include the risk of reversion of live mutant strains and poor immunogenicity of killed bacteria. The present disclosure provides a multivalent vaccine from whole cell extract that can be used for treatment and/or prevention of bacterial infection while effectively adjuvating the immune response.